A wheeled vehicle, such as a car or truck, that is propelled solely by an electric motor, sometimes referred to as a traction motor, that draws electric current from an on-board source of electricity, such as a battery bank, has a range of travel that is limited not only by how it is driven and the physical characteristics of the geographical area within which it travels, but also by the amount of on-board stored energy that the on-board source can deliver to the motor.
Because the propulsion system of such a vehicle lacks a combustion engine that is powered by fuel combusted in combustion chambers and therefore also lacks a liquid cooling system through which liquid coolant circulates to cool the engine, hot liquid coolant is unavailable for heating the interior of a cabin, or cab, for a driver of the vehicle. If the cabin is to be heated and windows are to be defrosted, another source of heat is used. Consequently, it is known to use electric heaters in such vehicles, but if such a heater draws electric current from the on-board source that also serves the electric traction motor that propels the vehicle, it does so at the expense of limiting the vehicle's range of travel for a given quantity of energy that is stored on-board at the start of travel.
If such a vehicle has an air conditioning system for cooling the cabin, that system too may draw electricity from the on-board source, and in doing so also limit the vehicle's range of travel.